Method of controlling undesirable vegetation



Patented July 11, 1961 2,992,091 METHOD OF CONTROLLING UNDESIRABLE VEGETATION Marion W. Harman and John J. DAmico, Nitro, W. Va., assignors to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Filed May 6, 1957, Ser. No. 657,051 25 Claims. (Cl. 71-245) This invention relates to methods of destroying or controlling vegetation and to herbicidal compositions. More particularly it relates to methods of destroying or controlling vegetation which comprises applying thereto a toxic concentration of a benzyl ester of a thiocarbamic acid containing the nucleus where X is a chalkogen'of atomic weight less than 40 at least one of which is sulfur.

General objects of the invention are to provide compositions which are toxic to living plants and to provide methods for their use to accomplish various desirable ends. A further general object is to provide compositions and methods for the destruction of noxious vegetation. Another object is to destroy noxious vegetation either in the form of germinating seeds or by application of the toxicant to the foliage after emergence. Another object is to provide a method for controlling broadleaved plants. A further object is to provide new compounds which are outstandingly effective herbicides and to provide methods for preparing them. A particular object of the invention is to provide toxicants which combine a hormonelike action on broadleaved plants and severe phytotoxicity to grasses.

A method of destroying or controlling undesired vegetation, according to this invention, comprises applying thereto a toxic concentration of a phytotoxic benzyl ester of a thiocarbamic acid containing the nucleus where X represents oxygen or sulfur at least one of which is sulfur and R represents benzyl, preferably halobenzyl, the number of halogen atoms being less than five. The halogen substituents are preferably chlorine but bromine and to a lesser extent fluorine and iodine are also suitable.

The acyclic esters of thiocar-bamic acids comprise grass specific herbicides but the benzyl esters are toxic to broadleaved plants. Certain benzyl thiocarbamates possessing structural characteristics hereinafter elucidated combine toxicity to both grass and broadleaves. Methyl substituted benzyl esters as for example p-methylbenzyl, o-methylbenzyl, 2,4-dimethylbenzyl and 2,6-dimethylbenzyl are also suitable.

The valences on the nitrogen are satisfied by hydrogen or organic radicals but not more than one aromatic radical may be linked directly to the nitrogen and'then the other radical is desirably an acyclic hydrocarbon of two or three carbon atoms. Divalent radicals forming with the nitrogen a closed heterocyclic ring are also con templated. Examples of amino radicals linked to the group are the radicals derived by removal of the hydrogen from the nitrogen of pyrrolidine, piperidine, S-ethyl- Z-methyl piperidine, morpholine, diethylamine, diisopropylamine and dibutylattiine. It is preferred that both of the remaining nitrogen valences in the nucleus are linked to carbon atoms.

The position of halogen is a significant variable. The compounds containing halogen in the 2- and 6-positions are outstanding. There may be a synergistic action from mixtures because the compositions from crude chlorination products have in general been equal or superior to any pure component known to be present.

The phytotoxic benzyl dithiocarbamates comprise weed killers having both pre-emergence and post-emergence activity. Accordingly, by applying the toxicant to the plant is meant any means whereby it is brought into contact with living plants which latter include germinating seedlings, as for example by application to the ground before the plants emerge or by direct application to the foliage.

The new toxicants may be applied conveniently in the form of a spray containing the active ingredient in a concentration within the range of (Ll-10.0% by weight. Thorough coverage of the foliage is effective for contact killing. For pre-emergence control of plants amounts within the range of A to pounds per acre may be used and within the range of 30100 pounds the compounds elfect soil sterilization. Examples of grasses which are controlled are foxtail, giant foxtail, annual blue grass, cheat grass, wild oats, rye grass and crab grass. Weeds from the following plant families are controlled to varying degrees: Leguminosae, Cucurbitaceae, Umbelliferae, Chenopodiaceae, Arnaranthaceae, Convolvulaceae and Aizoaceae.

Although most of the esters are insoluble in water, they are soluble in common organic solvents. Most of them are soluble in acetone, chloroform, ethyl alcohol, ethyl acetate, benzene, ether and heptane. The esters may be dispersed directly in water or a solution in an organic solvent emulsified in aqueous medium by the aid of a dispersing agent. As dispersing and wetting agents there may be employed soft or hard sodium or potassium soaps, alkylated aromatic sodium sulfonates such as sodium dodecylbenzenesulfonate, an amine salt as for example dibutyla-mmonium dodecylbenzenesulfonate, alkali metal salts of sulfated fatty alcohols, ethylene oxide condensation products of alkyl phenols, or tall oil or higher mercaptans and other dispersing and wetting agents. Formulation of dry compositions is accomplished by mixing with finely divided solid carriers. Suitable carriers comprise talc, clay, pyrophyllite, silica and fullers earth. Usually the toxicant will be only a minor proportion. The dry formulation may be used as a dust or dispersed in aqueous medium before application. If the latter it is convenient to incorporate a wetting or dispersing aid into the formulation.

The benzyl thiocarbamates exert formative effects like those commonly associated with the chlorophenoxyacetic acids. Herbicidal activity on foliage contact particularly against broadleaved plants is illustrated by the data record- ,ed.in Table I. It is believed that the acid component contributes toxicity to grasses and that the ester radical contributes the toxicity to broadleaves but the invention is not limited to any theory of the operation. A spray containing the concentration of the active ingredient shown in the table was applied to the foliage of grasses, to the foliage of bean plants and to the foliage of a mixture of broadleaved plants. The mixture is indicated in the table as Broadleaf. A rating of 0 indicates no phytotoxicity, 1 slight, 2 moderate and 3 severe phytotoxicity.

The compounds designated ar,ar,ar-trichlorobenzyl esters were derived from reaction of an alkali metal thiocarbamate with chlorobenzyl chloride prepared by chlo- Table l-Continued methyl)methyldithiocarbamate, dihydrate.

rlnating toluene in the ring in the presence of iron unt l Phytotoxicity Rating the gain in weight corresponded to that calculated for tri- A u I t 1 0., chlorotoluene and then removing the iron and chlorrnate ngre Grass Bean Broad. ing the side chain until the gain in weight corresponded l a to that calculated for trichlorobenzyl chloride.

2,4-Dichlorobenzyl diisopropyl- 0. 5; 3 -3 T able 1 dithiocarbamate. 0.2 2 1+ 2 3,4-Dichlorobenzyl diisopropyldithiocarbamate 0. 5 3 3 2 Phytotoxicity Rating 2,6-Dichlorobenzyl diisopropyl- 0. 5 2 1 3 Cone. dithiocarbamate. 0. 2 1+ 2 Active Ingredient percent ar,ar,ar-Trichlorobenzyl ditliiocarbam- Grass Bean Broadate 0.5 2 3 2 leaf 2,4, 5-1richlorobenzyl diisopropyl-di- 0. 5 2+ 1+ 2+ thiocarbamate. 0. 2 1 1+ 2,4,6-Trichlorobenzyl diisopropyl-di- Benzyl dimethyldithiocarbamate 1.0 3 r 3+ thiocarbamate 0.5 1 1+ 2+ ar,ar,ar-Trichlorobenzyl dimethyli ar,ar,ar-Trichlorobenzyl morpholinedithiocarbamate 0.05 1 1 1 carbodithioate 0.5 1+ 2 2+ ar,ar,ar-Trichloroben iethyl-di- 2,3,6-Trichlorobenzyl diisopropyldi- 0. 5 2+ 2+ 3+ thiocarbamate 0.5 1 3 2+ thlocarbamate 0.2 2+ 3 ar,ar,ar"lricl1lorobenzyl O-Sodium salt of ar,ar,artrichlorothiolcarbamate 0. 5 3 v 3 3 benzyl N-(carboxymethyD-methylar,ar,ar-Trichlorobenzyl diisopropyl- 0.5 1+ 2+. 2+ dithiocarbamate, dihydrate 0.5 1 3 3+ dithiocarbamate. 0.1 -2 2 3 O-Sodium salt of 2,3,6-trichlorobenar,ar,ar-Trichlorobenzyl diisobutylzyl N-(carboxymethyl)-methyldidithiocarbamate 0.5 0 1 2+ thioearbamate, dihydrate O. 5 1 2+ 3+ ar,ar,ar-Trichlorobenzyl dipentyl-dithiocarbamate 0.5 1 1 2 na a r h r v The data recorded in Table II demonstrate pre-emoxyethyhdlthiocarbamate .1 0.5 1 3 3 ar,ar,ar-Tr ichlorobenzyl N-allyl-isoergence activity. In these tests the spray was applied pmpyldllhlocarbamalem-. 1 2 to the ground of seeded plots before any plants emerged. ar,ar,ar-'lrichlorobenzyl diallyl-dithi carba ate 0, 5 2 3 3 The plants studied included most of the following 111 each ar,ar,ar-Trichlorobenzyl N-(Z-carbamoylethyncyclohexymithiocap test. Wild oat, cheat grass, rye grass (dom.), buckwheat, ama. 0.5 o 1 2+ mustard (rad1sh), red clover, beet-sugar, cucumber, cotar,ar,ar-Trlchlorobenzyl N-(z-chloroanyl)150mopyldithmatbamam n 0' 5 1+ 3 3 ton, corn, foxtail, portulaca, brome grass, barnyard grass, 0.5 1+ 3+ 2+ crab grass, field bmdweed, Russian thistle, pigweed and -g gggggtg dnsopmpyl wild morning glory. The quantity of the benzyl ester O-Chlorobenzyl p py 5 2+ apphed per acre is recorded together with the phytotoxicity carbamate. 0. 2 1 0 2 observed.

Table 11 Active Ingredient LbsJAcre Results Observed Benzyl dimethyldithiocarbamate Severe phytotoxicity wild oats, cheat grass, mustard and rye grass; moderate phytotoxicity to beet. ar,ar,ar-Trichlorobenzyl diethyldithiocarbamate 5 Mustard, clover, sugar-beet abnormal, slight formative efieot.

25 Severe formative effect on cucumber. 10 All broadleaf plants show severe formative effects at all rates ar,ar,ar-Trichlorobenzyl diisopropyldithiocarbamate 5 down to 1 lb./acre. All grasses severely injured at 25 lbs. and

2. 5 10 lbs/acre and to a lesser degree at decreasing rates. 2,4,5-Trichlorobenzyl diisopropyldlthiocarbamate. 25 Slight formative action. ar,ar,ar-Trichlorobenzyl morpholinecarbodithioate... 25 Severe formative efiects on all broadleaf plants. ar,ar,ar-Trich1orobenzyl dithiocarbamate 25 Formative efiects. Severe phytotoxicity sugar beet and pigweed; moderate phytotoxicity morning glory, mustard and field bindweed. 25 Formative action at all rates; wild oats, rye grass, clover, and p-Chlorobenzyl diisopropyldithiocarbamate 10 beet abnormal and stunted. All grasses abnormal. No crab 5 grass survived at 25 lbs. /acre. 25 Formative action. Wild oats, rye and foxtail abnormal and 2,4-Dichlorobenzyl diisopropyldlthiocarbamate 1% all bfioadleaved plants stunted at all rates. Foxtail destroyed a a re es. o-Ohlorobenzyl diisopropyldithiocarbamate 5 Formative action. Wild oats, rye, buckwheat, clover, cucumber abnormal. Complete control of foxtail. ar,ar,1=;tr-Trichlorobenzyl bis-(Z-methoxyethyl) dithio- 25 Severe formative action on all broadleaved plants.

car amate. ar,ar,ar-Trichlorobenzyl N-allylisopropyldithiocar- 25 Slight formative action on all plants.

bamate. ar,ar,ar-Trich1orobenzyl diallyldithiocarbamate 25 Severe formative action on all broadleaved plants. ar,ar,ar-'1richlorobenzyl dipentyldithiocarbamate- 25 Slight formative action on all plants. ar,ar,ar-Trichlorobenzyl N-(2-carbamoylethyl) cyclo- 25 Slight formative action on broadleaved plants.

hexyldithiocarbamate. ar,ar,ar-Trichlorobenzyl N-(2-chloroa1lyl)isopropyl- 25 Buckwheat, radish, clover, beet, cotton and cucumber all dithiocarbamate. abnormal.

5 Formative action. Wild oat, barnyard grass, crab grass and pigweed very abnorm 2,6-Dichlorobenzyl diisopropyldithiocarbamate 1 Grab grass and beet abnormal, pigweed dying. Severe phytotoxicity to wild oat, foxtail, barnyard grass, mustard, beet and pigweed. 5 Forrgative azgtiog. Wil li oats, foxtail, crab grass, bindweed an pigwee a norma 2,3,6-Trichlorobenzyl dhsopropyldrthiocarbamate. 1 Foxtau an $1 crab grass abnormal pigweed dying. Severe phytotoxicity to wild oat, foxtail and barnyard grass. 2,4,6-Trichlorobenzyl diisopropyldithiocarbamate. 5 Formative action. Wild oats, foxtail and pigvveed abnormal. 25 Foruativte actti)on evirllent on broadleaves, foxtail, crab grass an co on a norma ar'arrar'rrdcmorobemyl dlethyltmolcarbamate 1 Slight formative action. Severely phytotoxic to foxtail, crab grass and pigweed. O-Sodium salt of ar,ar,ar-trichlorobenzyl N-(car- 25 Slight formative action on broadleaved plants.

boxymethybmethyldithiocarbamate diliydrate. O-Sodium salt of 2,3,6-trichl0robenayl N-(carboxy- 25 Moderately severe formative action on all broadleaved plants Ar,ar,ar-trichlorobenzyl diisopropyldithiocarbamate is slowly lethal at rates as low as 2.5 pounds/ acre.

Tests were designed to measure the yield increase due to the herbicide and to determining whether the herbicide 6 Attapulgus clay. The resulting ar,ar,ar-trichloroberi'zyl diisopropyldithiocarbamate was a viscous oil obtained in 77.7% theory yield.

For the preparation of halogenated benzyl halides other injured the crop. The individual figures in Table III are 5 catalysts than light and other chlorinating agents than the average of the replicates indicated. The tests were elemental chlorine are suitable. A compound having run on corn, one series of treated plots being hand weeded similar properties results from SO Cl chlorination of tri- SO th t W ed c petition was not a factor. These hand chlorotoluene in the presence of peroxide. Distillation weeded Plots showed no significant e i i n from t e of the crude product yielded a fraction B.P. 106-108 0/ hand weeded check. The tractor cultivated plots and the 2 m, hi h gave a lid t Th t i hl b l djhand weeded Plots were adjacent to eaeh other 80 as to isopropyldithiocarbamate from this fraction melted at 71- be directly Comparable The difference is a measure of 73 C. after recrystallizing from heptane. It exhibited the yield decrease due to weed competition. The differno advantage over the composition prepared from un. ence between these decreases and that of the untreated di ill d i hl b fl hloride, check is the net increase due to the herbicide. The weight Ararar i hl b 1 di khi l b t was of Weeds Present at harvest given in the last column prepared as follows: A solution comprising 202.4 grams dicates the degree of weed control. The yield increase 2 0 moles) f 1 i d 500 1 of d h 1 in the hand weeded plots at 8 and 16 pound rates which ether was Cooled to 1 C d 120 grams (2 l Produced Perfect weed control may be due to better of carbon oxysulfide bubbled in at 10 to 0 C. over a aeration from hoeing around the plants. The ata in minute period or until a gain in weight of 120 grams. Table III we e Obtained using arena-trichlorobenzyl The reaction mixture was stirred at 0-10 C. for 1.5 hours isopropyldithiocarbamate. and then 230 grams (1.0 mole) of ar,ar,ar-trichloro- Table III Yield Yield Average No. of Hand Tractor Decrease Increase Wt. of Rate, Lbs.l Repli- Weeded Cultivated Due to Due to Weeds Acre cations Plots, Plots, Weeds, Chemical, Harvested BuJAcre BuJAcre BuJAcre BuJAcre Per Plot,

Lbs.

3 99 89 10 2e 0 3 107 86 21 15 0 4.-- 3 106 89 17 19 2.8 None-check--- 12 104 68 36 8.2

The halogenated benzyl esters of this invention may benzyl chloride added in one portion. The mixture was be prepared by condensing a halogenated benzyl alcohol maintained at 25-30 C. for 24 hours, filtered to remove with a thiocarbamyl halide to yield a thionocarbamate the amine hydrochloride and the ether removed in vacuo. and by condensing a halogenated benzyl halide with a Unreacted ar,ar,ar-trichlorobenzyl chloride was removed salt of a dithid or thiol-carbamic acid. A trichloro- 40 by heating at 1-2 mm. at a maximum temperature of benzyl chloride suitable for preparation of the preferred ISO-200 C. and the product filtered to remove a small composite product may be prepared by the following amounts of impurities. Adark amber viscous oil was obprocedure: Substantially 1500 parts by weight of dry tained in 82.7% theory yield. Analysis gave 3.23% toluene was charged into a chlorinator of suitable capacnitrogen and 9.57% sulfur as compared to 3.95% nitroity. Substantially 15 parts by weight of iron filings were gen and 9.04% sulfur calculated tor C H Cl NOS. added as catalyst carrier for ring chlorination and chlo- Substituting diisopropylamine in the foregoing prorine introduced at about 20 C. During the last part cedure yielded ar,ar,ar-triehlorobenzy1 diisopropylthiolof the run the temperature was increased to about 70 carbamate as a viscous amber oil. C. in order to keep the mixture fluid and the flow of Although some of the halobenzyl chlorides are new chlorine continued until the increase in weight correcompounds, they may be prepared by well known prinsponded to that calculated for trichlorotoluene. Thus, ciples of organic chemistry. a-2,4,S-tetrachlorotoluene when the product analyzed 54.8% chlorine, the fiow of was prepared by the chlorination of 2,4,5-trichlorotoluchlorine was interrupted and the trichlorotoluene given ene, 1,1 grams of benzoyl peroxide was added to 237 a 1 caustic W and filtered through a bed of y grams of 2,4,5-trichlorotoluene M.P. 82.5 C. dissolved in order to remove the iron. Alternatively, the iron may i 250 1, f bon tetrachloride. There was then be removed by distillation of the chlorinated product. dd d 164 grams f sulfuryl hloride. The solution wa The Product was then Chlorinated at ill the P heated up very slowly over a period of about 3 hours to ence of ultravoilet light until the gain in weight was that 77 C d th kept at refluxing temperature (77 C.) calculated for trichlorobenzyl chloride. Analysis of the f a Period f 4 hours. Th Solvent d ulfuryl h1 Product for chlorine at this Point gave ride were removed by distillation and the residue distilled Condensation with Sodium diisopl'opyldithioeafbamate in vacuo and then fractionated. a.-2,4,5-tetrachlorotolu- Was efle as follows: A Solution Comprising 202-4 one was obtained as a colorless liquid with a boiling point grams moles) of diisopfopylamine, 320-0 grams of 102-l04 C. at 2 mm. Hg. Condensation with sodi- T 0f 25% Sodium hydroxide and 1610 grams of um diisopropyldithiocarbamate yielded 2,4,5-trichloro- Water w C001edt0 and 1521) grams moles) 5 benzyl diiospropyldithiocarbamate in 98.5% yield. The of carbon disulfide added over a 30 minute period with product was a 1m y, 53 54 (3,, analyzing 3.80% a slight temperature rise T reaction nitrogen, 17.14% sulfur and 28.73% chlorine as comture was stirred for an additional 30 minutes and 460.0 d t 3 78% nitrogen, 17 29% ulfur and 28 69% grams (2.0 moles) of trichlorobenzyl chloride added in h i l l d for C I-I C1 NS One P a Slight temperature rise again being noteda-2,4,6-tetrachlorotoluene was prepared by adding chlo- The reaction mixture was then heated to 50-60 C. for fi to 723 grams of 2,4,6-t i h1 t 1 M P, 33 34 3 hours, cooled to 25 C., the water layer separated and C h i hl l was placed i a fl k equipped discarded- The P t layer was washed with Several with a stirrer, condenser, thermometer and a bubbler 200 cc. water washes, vacuum treated for 1.5 hours at tube and heated to 90 C. at which temperature 132 70:80 Q. under 5 10 pressure and filtered through of chlorine were added over a 2 /2 hour period.

7 It was necessary to supply a small amount of heat to hold the temperature between 190-198 C. during chlorination. The product was then fractionated and or-2,4,6- tetrachlorotoluene collected as a colorless liquid, boiling a-2,3,4-tetrachlorotoluene was prepared by light cat alyzed chlorination of 2,3,4-trichlorotoluene. 283 grams of the trichlorotoluene was heated to 180 C. and then with a sunlainp placed 8 to 10 inches from the pot, 50

point 123-126 C. at 8 mm. Hg. Condensation with grams of chlorine added over 40 minutes at 180 to 200 sodium diisopropyldithiocarbamate yielded 2,4,6-trichlo- C. The product was distilled in vacuo to yield Ill-2,3,4- robenzyl diis opropyldithiocarbamate in 77.5% yield. tetrachlorotoluene as a colorless liquid B.P. l37142 C. After recrystallization from ethyl alcohol the product t H Condensing ith sodium diisopropyldim d at 1 1 Analyse s mtrogen, thiocarbamate gave a 90.2% yield of 2,3,4-trichloro- 17.28% sulfur and 28-99% chlofllle as compared 10 benzyl diisopropyldithiocarbamate, a viscous oil. 378% mtrogen 17-29% sulfur and 28-69% chlorme a-2,5-trichlorotoluene was prepared by light catalyzed a1culated [if CBH16C13NS2' 1 chlorination of 2,5-dichloroto-luene in a manner similar In z l g' f g P to that described. The desired product was isolated by prepare y m ucmg grams 0 0 m o fractional distillation as a colorless liquid, B.P. l32l36 grams of 2,3,6-tr1chlorotoluene M.P. 41-42 C. at a tem- 10 C at 25 mm H 2 s dichlorobenz 1 diiso m 1dithio perature of ll98 C. The product was collected as t 1 77 m y f; a colorless liquid by fractional distillation M.P. 132- rme F obyle 6 n ensmg. W 135 C. at 10 mm. Hg. Condensation with sodium diisomm ilsopmpy cm ,locar amate' t was vlscous propyldithiocarbamate produced 2,3,6-trichlorobenzyl di- 011 'analyzmg 382% mtrogen as compared to a calm is'opropyldithiocarbama'te in 79.5% yield. The product 510 med value P 411% i was a solid M.P. 82-83 C. after recrystallization from The Physical1 Propemes of some of the PhYtOtQXIC heptane. Analysis gave 3.74% nitrogen, 17.23% 5111- ha10b@n Zy1 esters are forth below- The p y fur and 28.92% chlorine as compared to 3.78% nitrogen, P P unless OtherWlSe indicated are those of 17.29% sulfur and 28.69% chlorine calculated for purified products. All yields reported are of unpurified C H Cl NS 25 products.

Table IV Analysis Yield, Structural Formula M.P., 0. percent Oalcd., Found, percent percent p-Chlorobenzyldiisopropyldithiocarbamate $63 }s4-s5 96.3

CH2S(S) CN[CH(CH3)2]2 2,4-Dlchlorobenzyl diisopropyldithioearbamate N 4.16 3.78 amber oil 80.9

CH:S(S)CN[CH(CH3)]: @01 Cl o-Ohlorobenzyldiisopropyldithiocarbamate N 4.65 4.39 ..do 83.0

CHQS(S)ON[OH(CH3)I]2 01 m-Ohlorobenzyl diisopropyldithiocarbamate N 4.65 3.97 viscous oil 89.5

OHnB( Nl Hs)n]:

3,4-Dichlorobenzyldiisopropyldithiocarbamate 5 $2 }5961 96.0

OH;S(S)CN[CH(CH;):]1

Tabl I V-Continued Analysis Yield, Structural Formula M.P., 0. percent Calcd., Found, percent percent 2,3,4,5-Tetrahl0r0benzyl diisopropyldithiocarbamate N 3. 46 2.87 8283 98.0

OH1S(S)GN[CH(CH3)z]:

ar,ar,ar-Triehlorobenzyl -ethyl-2-methyl-l-piperidenicarbodithioate N 3. 5 3.0 brown viscous oil..- 88.0

0H2S(S) ON 1 Recrystallized from ethyl alcohol. 3 After tecrystallizing from ethyl alcohol. 3 After recrystallizing from ethyl acetate.

It is intended to cover all changes and modifications of the examples of the invention herein chosen for purposes of disclosure which do not constitute departures from the spirit and scope of the invention.

This application is a continuation-in-part of application Serial No. 470,836, filed November 23, 1954, now U.S. Patent No. 2,919,182, granted December 29, 1959.

What is claimed is:

l. The method of controlling undesired vegetation which comprises applying thereto a toxic concentration of a phytotoxic benzyl thiocarbamate possessing the structure where X is selected from a group consisting of oxygen and sulphur at least one of them being sulfur, and R represents a radical selected from the group consisting of benzyl, methyl substituted benzyl and halobenzyl containing not more than 4 halogen atoms and R represents an amino radical selected from the group consisting of pyrrolidinyl, piperidinyl, 5-ethyl-2-methyl piperidinyl, morpholinyl, N-fl-hydroxyethylpiperazinyl, NH and disubstituted NH wherein the substituents are selected from the group consisting of lower alkyl, lower alkoxy substituted lower alkyl, Z-carbamoyl ethyl, carboxy methyl, lower beta-monoolefinic, chloro substituted lower betamonoolefinic and six-membered carbocyclic radicals with the proviso that not more than one is carbocyclic.

2. The method of controlling undesired vegetation which comprises applying thereto a toxic concentration of a halogen substituted benzyl dithiocarbamate possessing the structure R-s-ii-N where R represents the halobenzyl radical and contains less than 5 halogen atoms, and R and R represent lower alkyl radicals.

3. The method of controlling undesired vegetation which comprises applying thereto a toxic concentration of a halogen substituted benzyl dithiocarbamate possessing the structure where R represents the halobenzyl radical containing at least 2 but less than 5 halogen atoms 2 of which are in the 2- and 6-positions, and R and R" represent lower alkyl.

4. The method of controlling undesired vegetation which comprises applying thereto a toxic concentration of a chlorobenzyl thiolcarbamate possessing the structure where R represents the chlorobenzyl radical containing less than 5 chlorine atoms, and R and R" represent lower alkyl.

5. The method of controlling undesired vegetation which comprises applying thereto a toxic concentration of a chlorobenzyl dithiocarbamate containing less than 5 chlorine atoms in the benzyl radical, the valences on the nitrogen in the dithiocarbamic acid nucleus being satisfied by alkyl radicals containing 3 carbon atoms.

6. The method of controlling undesired vegetation which comprises applying thereto a toxic concentration of trichlorobenzyl diisopropyldithiocarbamate.

7. The method of controlling undesired vegetation which comprises applying thereto a toxic concentration of a 2,5-di-chloro substituted benzyl ester of a di(lower alkyl)dithiocarban1ic acid.

8. The method of cont-rolling undesired vegetation which comprises applying thereto a toxic concentration of 2,5-dichlorobenzyl di-alkyldithiocarbamate wherein each alkyl group contains at least two but not more than three carbon atoms.

9. The method of controlling undesired vegetation which comprises applying thereto a toxic concentration of a meta chloro substituted benzyl ester of a di(lower alkyl)dithiocarbamic acid.

10. The method of controlling undesired vegetation which comprises applying thereto a toxic concentration of m-chlorobenzyl diethyl-dithiocarbamate.

11. The method of controlling undesired vegetation which comprises applying thereto a toxic concentration of a 2,6-di-chloro substituted benzyl ester of a di(lower alkyl) dithiocarbamic acid.

12. The method of controlling undesired vegetation which comprises applying thereto a toxic concentration of 2,6-dichlorobenzyl di-alkyldithiocarbamate wherein each alkyl group contains at least two but not more than three carbon atoms.

13. The method of controlling undesired vegetation which comprises applying thereto a toxic concentration of 2,4,6-trichlorobenzyl dialkyldithiocarbamate where 1 each alkyl group contains at least two but not more than three carbon atoms.

14. The method of controlling undesired vegetation which comprises applying thereto a toxic concentration of 2,3,6-trichlorobenzyl dialkyldithiocarbamate wherein each alkyl group contains at least two but not more than three carbon atoms.

15. The method of controlling undesired vegetation which comprises applying thereto a toxic concentration of 2,3,4-trichlorobenzyl dialkyldithiocarbamate wherein each alkyl group contains at least two but not more than three carbon atoms.

16. The method of controlling undesired vegetation which comprises applying thereto a toxic concentration of a chloro substituted benzyl ester of a di(lower alkyl)thiolcarbamic acid the number of chlorine atoms being at least one but less than five.

17. The method of controlling undesired vegetation which comprises applying to the soil medium before the plants to be destroyed emerge a toxic concentration of a polychlorobenzyl ester of a di(lower alkyl)thiolcarbamic acid in which the ester radical is composed of mixed isomers of polychlorobenzyl containing an average of 3 chlorine atoms.

18. The method of controlling undesired vegetation which comprises applying to the soil medium before the plants to be destroyed emerge a toxic concentration of a polychlorobenzyl ester of a di(lower alkyl)dithiocarbamic acid in which the ester radical is composed of mixed isomers of polychlorobenzyl containing an average of 3 chlorine atoms.

19. The method of claim 1 in which the toxicant is applied to the soil medium before the plants to be destroyed emerge.

20. The method of claim 2 in which the toxicant is applied to the soil medium before the plants to be destroyed emerge.

21. The method of claim 3 in which the toxicant is applied to the soil medium before the plants to be destroyed emerge.

22. The method of claim 4 in which the toxicant is applied to the soil medium before the plants to be destroyed emerge.

16 23. The method of claim 5 in which the toxicant is applied to the soil medium before the plants to be destroyed emerge.

24. The method of claim 6 in which the toxicant is applied to the soil medium before the plants to be destroyed emerge.

25. The method of controlling undesired vegetation which comprises applying to the soil medium before the plants to be destroyed emerge a toxic concentration of a compound possessing the structure 2,060,733 Hunt et al Nov. 10, 1936 2,160,880 Loane et al. June 6, 1939 2,562,011 Baumgartner July 24, 1951 2,642,451 Weijlard June 16, 1953 2,650,876 Stewart Sept. '1, 1953 2,687,348 Kosmin Aug. 24, 1954 2,710,259 Blake et al. June 7, 1955 2,723,989 Harman Nov. 15, 1955 2,744,898 Harman et al. May 8, 1956 2,776,196 Gysin et al. Jan. 1, 1957 2,776,197 Gysin et al. Ian. 1, 1957 2,812,247 Gysin et al. Nov. 5, 1957 FOREIGN PATENTS 858,352 Germany "1-1-"..- Dec. 4, 1952 OTHER REFERENCES Templeman et al.: Nature, vol. 156, November 24, 1945, page 630.

Shaw et al.: Weeds, January 1953, pages 43-65.

Szabo et al.: Chemical Abstracts, vol. 51, 1957, col. 2217. 

1. THE METHOD OF CONTROLLING UNDESIRED VEGETATION WHICH COMPRISES APPLYING THERETO A TOXIC CONCENTRATION OF A PHYTOTOXIC BENZYL THIOCARBAMATE POSSESSING THE STRUCTURE 